jury-rigged storm window

[ryanwc]

Folks,

We have a back room designed by previous owners off our kitchen. It was sold as a "3-season room." It's probably 14 x 14, with rows of 4 windows on each side and a glass exterior sliding door and 2 windows at the back. It's connected to the kitchen by an indoor sliding door.

It presents a few challenges. Because the kitchen door isn't at all air-sealed, it's effectively winter 'indoor' space, yet it would be very expensive to actually heat because it's so leaky and/or exposed/uninsulated. With the kitchen door closed, it's much closer to outdoor air temps than to indoor temps, but lots of cold air comes around the door, keeping the kitchen floor pretty cold.

The windows are a source of both leakage and radiative heat loss, though they're theoretically efficient, double-paned windows. We've hesitated to spend the money for storms, because we're not sure how much it would help, given other potential sources of air leaks and radiation.

But there are existing screens. I jury rigged a storm using a shrink-wrap window sealing kit, wrapped around a storm. I put this screen in the 3rd window from the house on the north side, and used my Flir infrared camera phone attachment to profile the various windows. With outdoor temps of about 32 and kitchen temps of 69, the windows on the south side ranged from 44 to 41, dropping by a degree as you went a window further from the wall. The windows on the north side had a similar pattern, except the window with the jury-rigged storm was about .75 degrees warmer than its neighbor one slot closer to the house. The Flir doesn't always match actual temps, but the relative temps can be trusted, and the general pattern of this room being about 2/3 of the way to exterior temps is accurate.

It seems like this jury-rigged storm is making a difference - arguably, that window was about 1.75 degrees warmer than expected. My questions are, how meaningful is this difference in terms of overall temps in that room? Would improving all the windows make a noticeable improvement?

And do you think shrink-wrapped plastic can last even one season of exposure to the outside? I have a feeling pressure differences on a windy day might shred the plastic. Or pull it out of it's "plunger-pin" slots .

Ultimately, if the experiment works, it would give us the information on whether it's worthwhile to have storms made and installed.

 

[Connecticut Yankee]

Isn't the shrink wrap intended to be installed inside? That's the only way I've ever seen it done, anyway. But if you're putting it outside merely for the sake of the experiment, I'd go ahead and seal all the screens, just to see what kind of difference it made.

But perhaps it might be more effective to do what you can to insulate the kitchen wall and improve the sealing of that door, so that at least the kitchen will stay comfortable.

 

[semipro]

Is the intent of the shrink wrap to better air seal the windows or provide increased thermal insulation or both?
From your description, I'd say that air sealing the porch would be far more productive than trying to improve window glazing R-value.
Your temp readings of the windows will be more accurate if you apply some painters tape first and take your readings there.
I've used the shrink wrap for years on various applications but doubt it will hold up well on the outside of your windows. I've found it to be fairly fragile.
Check this out also: https://www.builditsolar.com/Projects/Conservation/bubblewrap.htm
It's about installing bubble wrap inside windows for insulation. I'm planning to give it a try soon (if it actually ever gets cold again. )

 

[ryanwc]

Thanks to you both. (Edited - And thanks for the painter's tape recommendation. I'll try that.) My intent is mostly air-sealing, because I believe the windows don't seal well. Although creating an air pocket, even a big one, between the window and the shrink wrap also has some insulating value. Yes, I understand that shrink wrap is intended to be used inside. There are two issues - first, to use it inside the main window would require using the double-sided tape on exposed (unpainted) wood trim of the room, and in my experience that tape doesn't come off. And second, it's not possible to use the shrink wrap on the inside face of the screen, which would give it a bit more stability, because I need access to the plunger-pins in order to put the screen in place.

My intent isn't a long-term use of shrink-wrap. The idea is just to use the shrink-wrapped screen as a proxy for a proper storm window, to see how much difference it makes.

I did a round of sealing. It had some effect - it used to be that the kitchen sliding door would scrape badly when you opened it in the winter, presumably because some expansion of either the framing or the door itself bent something. After the sealing, that no longer happen, presumably because the inner and outer faces of the doorway are in closer temperature alignment. But even if the room is somewhat closer to indoor temps, it's didn't make enough difference to make it inhabitable for much more of the year. I'm not sure where else I could easily air seal. The energy auditor told me the r-value of the wall isn't great.

The storms were quoted at $80/window, times 10 windows, plus installation that he estimated at $150, to mount the clasps that would hold the storms. If $950 made the room inhabitable an extra 2 months/year, it would be worthwhile, but if the impact isn't that great because the r-value of the walls, or air leaks I haven't found, are more important to the temps, then it's not worth doing the storms. The plastic wrap seemed a way to test the value of storms.

 

[Connecticut Yankee]

It's an interesting problem. I would love to know the results of the "storm window" experiment, but I fear they won't be all that encouraging. If you want to use that room for more months of the year, it sounds as though the best course might be to knock it down and rebuild. If your goal is merely to improve the kitchen temperature, however, that might be possible with a less drastic solution.

Am I right in guessing that this glass room is on the north side of the house and is exposed to the prevailing winds? Because otherwise I'd expect you to be getting more of a greenhouse effect than you are evidently getting. Good luck getting it all figured out.

 

[ryanwc]

I had two pieces of the shrink wrap from an earlier project. I installed a second wrapped screen last night, and tested it this morning. The temp readings seem to bear out the idea that this making a difference.

Though I really need to use the camera at night. The difficulty of getting accurate reads on glass seems exacerbated in daytime since the backdrop - the neighbor's house, has varied exterior treatments. I try to take readings from angles that minimize the differences, but it all adds up. The camera regularly recalibrates, so it's not clear that taking actual photos and then comparing them in an absolute way would be meaningful. And a wide-angle shot of more than one window puts different backdrops behind various windows. So what I'm doing is just using it as a handheld scanner that I read live. I do it a few times, and come up with a decent sense of how the readings change from window to window, even if I don't consider any single set of snapshots as definitive.

Anyway, for now, I'm seeing enough of a difference that I think I'll continue by buying another shrink-wrap set, which should get me 3 more windows.

 

[ryanwc]

Am I right in guessing that this glass room is on the north side of the house and is exposed to the prevailing winds? Because otherwise I'd expect you to be getting more of a greenhouse effect than you are evidently getting. Good luck getting it all figured out.

I've been surprised there isn't more of a greenhouse effect as well. It's at the east end of the house. It's a bit more than half the width of the house itself, on the north side in that sense. There is a maple to the east and the sun is shining through its bare branches much of the morning. By midafternoon, the sun is behind the house.

But even at midday, the sun doesn't do much for this room during the winter.

There's another aspect - there is a small air gap between the brick rear wall of the house proper and the 3-season room. In a sense, it's an island surrounded by 4 exterior walls.

Knocking down and rebuilding isn't likely. We could afford it I guess, but I'm not sure the cost-benefit ratio would justify it. A less drastic solution might be to pull away the exterior aluminum siding, apply some sort of Tyvek and perhaps insulation, then re-side. Though that's just my amateur viewpoint, not something anyone has told me would work.

 

[semipro]

When I recommended the use of painters tape I was thinking you were using a laser type temp gauge not an IR camera - sorry.

 

[begreen]

I used heat shrink, interior storm windows with double-stick, 3M tape for several years before replacing the windows. Done properly they are very effective.

 

[woodgeek]

OK, the answer depends on what you want to achieve.

It seems your biggest problem is cold kitchen floor. Rather than upgrading the LARGE area of windows and doors in the glass room, your best bang for the buck/effort would be to just improve, airseal or replace the slider to the kitchen....it is a much smaller area. Without a heat source out there, the temp out there will still follow the outside (more or less) and the kitchen slider will still see a heat loss.

DIY airsealing, or inspecting/insulating the surround, or replacing with a modern, low-e unit could have a big effect.

I grew up with one of these rooms, built by my (professional builder) Grandfather and (v handy) Dad. They insulated it well, and put in Anderson double panes. We would use it during winter holidays, and just run a space heater out there a few hours to bring it up before we opened the slider. Easy. When the guests went home, the room went cold.

 

[ryanwc]

An interesting result. With the recent cold temps, the windows with my jury-rigged plastic wrap storms have no ice, but the others have frost in the margins.

It's hard to quantify exactly because there are many factors, but they definitely have an effect. Our kitchen isn't leaking heat the way it once did.